A number of recent chip sets have Peripheral Component Interconnect Express (PCIe) buses for achieving fast-speed data transmissions. Meanwhile, a number of Redundant Arrays of Inexpensive Disks (RAID) apparatuses are often configured from multiple units, wherein the units are connected through midplanes, backplanes, and cables.
Among those, cables are employed for connections between enclosures. Although it is preferred that the lengths of cables employed for inter-enclosure connections are adjusted to optimum lengths in accordance with the distances between enclosures, the distances between enclosures depend on floor plans and thus cannot be determined unconditionally.
Additionally, in fast-speed data buses, waveforms are also required to be adjusted. The waveform adjustment is done by appropriately changing and setting the values of the output voltage, the input equalizer, and the output pre-emphasis, for example. If such values is too large or too small, the transmission quality reduces. Hence, it is important to set optimal values in accordance with the transmission distance and other parameters.
Some of devices including PCIe buses have a function to automatically adjust waveforms upon a connection. However, unlike PCIe, no standard for automatic adjustments of waveforms has been stipulated for optical cables, and thus no automatic adjustment of waveforms is available for optical cables. Even with Cu (copper) cables, stable connections may not be achieved under the influence of noises or other factors, due to device compatibility and device deviations.
Accordingly, in conventional RAID apparatuses, cables employed for inter-device connections have been limited and waveform setting values fixed for those cables have been set.
Patent Document 1: Japanese Laid-open Patent Application No. 2014-2637
Patent Document 2: Japanese Laid-open Patent Application No. 2005-339983
However, since only limited cables are employed in conventional RAID apparatuses, configurations employing such communication cables are not flexible in design and thus are inconvenient. For example, long cables are used even for connections between adjacent devices.